The sun...
Gives us warmth and light.
It is the fuel of life.
Without the energy of the sun almost nothing grows, thrives or lives.
But the sun was not put there for our benefit.
It is not this big jolly ball of nice smiling down on us,
wishing us all a good day.
It is not our friend.
The sun is a monster.
A planet killer.
And we don't see that side of the sun down here.
But eight astronauts,
with over 1,000 days in space between them,
Can show us how being up there
helped them understand the suns bright fury.
It's got an incredible amount of power which you
really appreciate when you go out in space.
Just like the gods of old,
the sun can give life
and it can destroy life.
It's a mean son of a gun.
It's exploding and it's sending cosmic radiation at us.
Given the amount of radiation from the sun,
there shouldn't be life on the surface of the earth.
We shouldn't be here.
But we are here.
And we owe our lives to this world.
I'm gonna tell you how the earth's core...
The air above us....
and life itself
work to protect us.
The earth shields us in a suit of armour.
And the way she does it...
Is one hell of a strange story.
You see that guy in the crowd?
He's just a bit different from the rest of us.
He's a spaceman.
Once he risked his life
to fix a telescope
350 miles above the earth.
And he's spent a lifetime
studying the stars.
People still feel this incredible fascination with,
with looking at the sun.
Twice a year
it just crosses the line of the cross streets of Manhattan...
And sets at just that right point that it just makes a
beautiful orange glow which permeates the city.
In some sense I suppose I could say I saw more of the
true character of the sun...
Than people who are always on the surface of the earth.
You open the airlock
and then turn around and look up.
It's like that great scene in the Wizard of Oz where Dorothy
comes out of the house and it's not black and white anymore.
All of a sudden, the whole world is in colour.
But don't forget those visors.
They do come in handy when that big fire ball is staring at you.
Yep.
One of my great eureka moments was realizing for the first time
when I was in space that I was seeing the sun in a black sky.
Think of that.
You really see the sun
as a star.
Particularly when I was out in the space suit,
the power of the sun just hits you in the guts.
It just goes through your entire body.
The temperature extremes are
250 degrees in the sun
and then minus 250 in the shade.
That's pretty incredible and that our suits can
withstand those temperatures.
But even we astronauts,
only experience a fraction of the sun's power.
It has many weapons it can send our way.
Heat, light
and deadly flares that can devastate entire planets.
Look at Mars.
Billions of years ago we think it was just like us...
A potential cradle for life.
But radiation from the sun ravaged it.
Solar flares with the destructive power
of billions of Hiroshima atomic bombs
helped chew away Mars's atmosphere
and the oceans evaporated into space.
Earth is even closer to the sun than Mars,
so how come we're not dust and ashes?
See, the thing is, our planet is strong on defence.
And every player has a role.
From the edge of space...
To the deepest oceans...
To one of the most hostile places on earth.
We'll be sleeping with gas masks on.
Sometimes it'll clear up and be beautiful
but most of the time we'll be wearing our gas masks even to bed.
Ken Simms doesn't do nine to five.
This is his idea of a good day at the office.
For over 20 years he's ventured into active volcanoes
across the globe
to collect samples of molten lava.
Studying this stuff is one of the best ways to understand
what's happening in the centre of the earth
and the process that protects us from the sun.
Pretty much that whole bottom
terrace now is completely covered in brand new lava flow, isn't it?
Yeah.
And with the new lava flow coming around against the wall there,
we'll have to watch out.
The lava's intensely hot,
roughly 2,000 degrees.
It will burn pretty much anything on contact.
Okay, heading over.
I'll go over just towards the edge here.
We'll have a look.
Whoa.
Holy...
It's just opened up on that side, hasn't it?
Yeah, totally.
Whoa.
Yeah, Ken, I'm pretty certain
that there is absolutely no way we are going down there.
That is without doubt mission impossible.
Okay, well, we're cancelling this mission.
Yeah.
Just anybody with half a brain wouldn't go down there.
The new vent means Ken can't take samples from the lake,
but he doesn't need to.
The vent is firing fresh lava right at him.
There's a lot of lava bombs around here.
It's just covered with bombs.
Wow, I'm... can see the vent from here.
It's really rocking and rolling.
I'm gonna head back up, over.
Sure, I'll come back.
The solid lava samples we've collected are radioactive.
They have uranium and thorium in them.
Those elements are really important
for maintaining the heat of the earth.
But wait a second.
What does any of this have to do with keeping us safe from the sun?
Radioactive lava up here
proves there's a raging nuclear furnace
at the heart of our planet.
It is one big ball of incredible heat.
I mean, a very big ball.
But that's not all.
These molten insides are full of iron and nickel.
Rising, falling, spinning in a constantly melting furnace.
And all that churning metal creates its own magnetic field.
This magnetic field stretches as far as 400,000 miles into space...
surrounding the entire planet.
It is a massive force field
and it helps deflect the deadly radiation
that destroyed Mars.
For the most part our magnetic field is invisible.
But when the sun flares up,
we get to see it in action.
We call it the aurora.
It's pretty much on everyone's bucket list
but in space,
you see it in an entirely different way.
I saw this green glow.
It's almost like a
person dancing. It was a shape and these forms that were moving
as we went over.
And the greens and reds and all of the faint colours,
like this enormous ghost of a curtain.
You're not just seeing it with your eyes.
It, you're feeling it.
You're feeling it with your heart as well.
It's a part of you.
When we look down at the aurora,
it's all the more beautiful,
because we know that we're looking at our planet
keeping us safe from the sun.
But you know what?
It takes more than that one shield to keep us alive...
because the sun has another weapon.
A silent assassin.
The assassin's name?
Light.
Everything revolves around the sun.
Literally.
It's the big boss of the solar system
but its most deceptive weapon
is something we usually think of as our friend.
Light.
It's a hazard astronauts need special protection from.
We see the visible light from the sun
but there's also ultraviolet light.
That can actually do significant damage.
Every porthole window has special layers, different UV filters.
On space station MIR there was one that was not.
But when I floated over that thing,
if you sat there and had those rays of sun hit you,
in less than a minute,
you'd see your skin reddened.
The power of UV light in space,
means that without our gold visors,
our eyesight could be damaged permanently.
For almost all life on earth,
facing the sun as we do in space,
would ultimately be fatal.
It's crazy, right?
In space you need a $12 million spacesuit
to protect you from the sun...
whereas on the surface of the earth,
just some lotion does the job perfectly fine.
We're quite fortunate.
Only about 2% of the really damaging ultraviolet radiation
from the sun actually gets down to the surface.
If every bit got down to earth...
skin would burn in a matter of seconds.
That's just the start.
UV radiation breaks down DNA
and turns healthy cells cancerous.
If we were hit by the full force of the sun,
plants would be sterilized...
microscopic life would be sterilized...
life couldn't be sustained on the surface of the earth.
Ultraviolet light
is vicious.
So how come we're not burned to a crisp?
The answer is high above us.
The sun slings deadly UV light at us...
but most of it is stopped in its tracks by a thin blanket
of molecules that we call the ozone layer.
The ozone layer is our second shield in the sky
but it's fragile,
extremely fragile.
30 years ago, we discovered man made chemicals
had punched a hole in the ozone layer.
Is that hole here to stay?
Waiting around to kill us?
Today we're trying hard to find out.
Morgan Sandercock is about to test
an experimental plane perfect for sampling ozone.
Go ahead, go, pressurizing.
We think we can go as high as 90,000 feet.
Jim, you're ready to go.
I'm ready.
That's the big boy territory.
That's where things can wrong very, very quickly.
If we lose cabin pressure,
then the pilots
could very easily pass out
and we don't have any automatic systems to recover from that.
Getting ready to roll.
Now a glider might sound like a dangerous choice so high up,
but gliders don't have engines
which means they can't pollute the team's samples.
Got a firm count, dolly off.
Count, dolly is off, wing wheel is off.
Okay, rolling at 11:32.
11:32, written down, if you can get us the time.
Airborne.
The Perlan glider uses air rising over the southern Andes
to reach extraordinary heights.
Air speed, 70 knots.
Looking beautiful,.
-Traffic. -Yeah.
52,000 feet up makes this the highest glider flight ever.
But you've gotta get this high to get a great picture of the ozone layer.
The good news is that thanks to a global ban
on ozone harming chemicals,
it looks like the hole is healing up.
Our shield is regenerating.
Our planet is not an inanimate object.
It's a living thing and it can heal itself.
When we discovered the hole in the ozone layer,
mankind did come together on that one and we banned those substances.
You look down and you see this fragile planet
which supports life on its surface
in the face of the incredible hostility
and so you become much more sensitive,
I think, to the need to protect it.
Any way you look at it, the ozone layer is pretty special.
This shield has looked after us for millions of years,
even before mankind came down from the trees,
even before the dinosaurs walked the earth.
Without the ozone layer,
there would be no human race.
Life on earth would be trapped under water.
In Earth's battle with the sun,
the sun has often had the upper hand.
Today the ozone layer protects us from UV,
but once upon a time, it wasn't there.
The only safe place for life was under the waves.
Life would probably still be down there
if it wasn't for something new
that emerged nearly three billion years ago,
and found a way to use sunlight to its advantage.
Billions of years ago,
as ancient organisms first harnessed the energy of the sun,
they began producing a waste product.
Oxygen.
At first it was just a few individuals,
but thousands became millions.
Millions became trillions.
All bubbling up oxygen.
When oxygen gas rises high into the atmosphere,
something very special happens to it.
It transforms into protective ozone.
Under the shelter of this ozone layer,
first microbes,
then fungi and plants
migrated out of the water.
And this meant even more oxygen was being produced,
further strengthening our shield against the sun's UV light.
And this would help make possible
one of our planet's most defining moments.
Protected by a thicker ozone layer than ever before,
a whole new world of possibilities opened up for life on earth.
We think it was about 400 million years ago,
when simple vertebrates
first took their tentative steps onto dry land.
It's probable that
these early animals
were moving around using something
that was still pretty much like
the fins that they used to get around in the water.
With that one small step from water to dry land...
life on earth changed forever.
That was one small step for animal kind
and one giant leap for life on earth.
Life spilled out of the water in a billion different ways
taking on a host of forms.
All because of that special layer of oxygen up in the sky.
Right, so that's two shields that our planet gives us.
But the sun has a final weapon.
Heat.
It's pumping out millions of degrees of powerful burn
and that powerful burn is intensified
by an ally down here on earth,
one feared by people everywhere.
Volcanoes make terrible neighbours
but even if you live far away from one,
like on the other side of the planet,
a volcano could still make you feel the heat.
Much of this gas cloud is CO2,
carbon dioxide,
and CO2 is a killer.
It traps heat in the atmosphere.
If you wanna know how dangerous CO2 can be,
just try taking a walk on Venus.
The surface of Venus is
hotter than hell.
Surprisingly the planet with the hottest temperature
at the surface in our whole solar system
is Venus,
even though it's not the planet closest to the sun.
That is purely the effect
of having too much carbon dioxide in your atmosphere.
On earth volcanoes have been firing
CO2 into the sky for billions of years.
So, here's the question.
How come it's pretty cool here on Earth,
while Venus is fully baked?
Well, the earth
has its own way of dealing with CO2,
unique to this planet.
But it can easily go wrong.
The sun threatens us with solar explosions
and ultraviolet light
but its most dangerous weapon
could be plain old heat.
It can cook planets,
especially ones wrapped in a warm blanket
of carbon dioxide gas.
But the Earth has its own very elegant way
to stop itself from being boiled dry by the sun.
The best way to see it in action
is from 250 miles straight up.
Just like the human body
has ways of keeping all of our systems in check,
similarly the earth has its own regulatory system...
and it's kept just about the right amount
of carbon dioxide in the atmosphere.
From space you got a unique perspective.
The process starts
with something no other planet in the solar system has.
An air conditioning system
made possible by rain.
Normally we think of the rain as being pure water
coming down out of the sky
but actually it's carrying dissolved carbon dioxide
from the atmosphere and
this makes it acidic enough to dissolve rocks.
Ultimately this water, silt
and locked-up carbon dioxide
will all get washed into the planet's rivers.
This process goes on right under our noses every day
but sometimes,
it can make itself visible in a truly spectacular fashion.
These people get to take a small peek at the way
our world keeps itself cool
and, wow, is it impressive.
Hidden in all that water is carbon
pulled from the sky.
This great river is forcing it into the ocean.
Seen from above,
its raging majesty is laid out for the stars to see.
Looking at rivers from space
you really get a sense
of the movement of huge amounts of material.
It's unforgettable.
You can see the brown colour which goes way,
way out into the ocean.
As rivers spit out huge quantities of sediment
and locked-up CO2,
carbon that was once in our atmosphere
gets buried at the bottom of the ocean
and that helps cool down our planet.
Over millions of years,
the cycle of rain, rivers and volcanoes
has helped balance the CO2 in our atmosphere,
keeping us warm in the coldness of space
while preventing us from being boiled alive by the sun.
I had studied earth science
but when you actually go into space
you feel it on a visceral level.
You realize it's the living Earth.
All of these systems on the planet
whether it's, you know, volcanoes, whether it's
currents in the ocean...
are shaping and moulding this planet that we see.
It looks like it's its own organism.
Like it's living, it's breathing, it's...
the... as the clouds move, I mean, it's almost like it's...
it looks alive.
Nature's ancient systems
have kept our planet safe
for billions of years
but now they're changing in a very big way.
Right now humans are pumping 60 times more CO2
into our atmosphere than volcanoes
and there isn't enough time
for the Earth's air conditioning system to correct the problem.
The planet is getting hotter.
How much hotter?
That depends on us.
It's not gonna be easy.
But my hope is that just as we fixed the ozone hole,
humans are ultimately gonna be able to fix this.
Human beings don't have to just stand by
and watch Earth's war with the sun.
We can help.
We have to.
For almost four billion years,
our planet has held off the power of the sun,
but that fire ball will get us in the end.
And thanks to Jeff Hoffman,
we've been given a terrifying glimpse into the future.
A very bright future.
For almost four billion years,
our planet has shielded us from the sun.
But those shields won't protect us forever.
Ask Jeff Hoffman.
He was part of the team
who allowed us to see our ultimate fate
when he helped fix the Hubble telescope.
Hubble couldn't see straight.
It was the butt of jokes of late night comedians.
It was denounced in the halls of the US Congress as a techno turkey.
It was a disaster.
So fixing Hubble
was critical for the future space activities
that NASA wanted to carry out.
We are inspired. We are ready. Let's go fix this thing.
Both as an astronomer and an astronaut to take my two hands and
put them on the Hubble space telescope and actually fix it...
Endeavoured motion of the aperture door.
Roger, we're alive.
That's been a great source of satisfaction.
We have a good release.
Copy. And we very much appreciate it.
I do have some good news for you, Jeff.
The payload folks have gone through a complete checkout
and are fully functional.
Great news.
Thanks to Jeff and the team,
Hubble went from turkey to triumph.
Some of these images are almost biblical in their intensity.
They still give me goosebumps when I look at them.
So many different forms and colours,
it looks like the work of some psychedelic artist
but it's the universe that we live in.
I mean, it's extraordinary.
The work on Hubble meant we could capture the exact moment
when a star like the sun dies.
Around five billion years from now,
the sun is going to grow in size,
swallowing up the earth.
And in those final moments,
all matter on our planet,
all traces of life...
will be torn apart
as the Earth is enveloped by the sun.
When I came back on Earth
and looked up at the sun,
it looked the way
it had always looked before
except I knew
that I had seen it
like it really was.
It's like
seeing somebody's true nature
very briefly when they let their guard down
and then you never see that again.
Earth's protected us from the sun for billions of years.
It's been one of the main reasons that life
has been able to thrive here on the surface.
As a biological creature we need the Earth to protect us
and these shields provide
sort of a blanket over us to just keep us secure
and sort of carefree on the planet.
Were we just lucky
that all these things happened to be in place?
Well, of course if they weren't in place,
we wouldn't be here and I wouldn't be talking about this.
Next time you take a walk outside when
the sun is high in the sky...
take a moment and think about the iron
churning at the Earth's core,
the oxygen bubbling out from under the sea, the rain
crashing onto the rocks,
all these things that came before us
and made this world possible,
those chance events, those planetary systems
that allow our little moat of dust to survive in a sunbeam.
You, me and everyone we know, we're lucky,
lucky to get as far as we have
and lucky to be here now.
But this is not the end of the story.
What's up? How are you doing?
Next time how all life on Earth got started.
And let me tell you,
that takes strange to a whole new level.